我需要在子类中复制我的类型注释吗？

Question

我有一个定义方法Base的eggs_or_ham类。

我是否需要在我的子类Foobar中复制类型注释，或者足以将它们添加到Base类中？

class Base:
    # ...

    @classmethod
    def eggs_or_ham(cls, eggs: List[Egg], ham: List[Ham]) -> List[str]:
        raise NotImplementedError


class Foobar(Base):

    # should I write this
    @classmethod
    def eggs_or_ham(cls, eggs: List[Egg], ham: List[Ham]) -> List[str]:
        # ...

    # or this
    @classmethod
    def eggs_or_ham(cls, eggs, ham):
        # ...

Answer 1

您需要（很好，应该）复制它们；至少mypy不“继承”类型提示。

给出一个简单的例子

from typing import List

class Base:
    @classmethod
    def foo(cls, eggs: List[str]) -> List[str]:
        return ["base"]

class Foo(Base):
    @classmethod
    def foo(cls, eggs) -> List[str]:
        return ["foo"]

print(Foo.foo([1,2,3]))

将进行类型检查，因为没有为Foo.foo的eggs参数提供类型提示。

$ mypy tmp.py
Success: no issues found in 1 source file

[添加类型提示（eggs: List[str]）会产生预期的错误：

$ mypy tmp.py
tmp.py:15: error: List item 0 has incompatible type "int"; expected "str"
tmp.py:15: error: List item 1 has incompatible type "int"; expected "str"
tmp.py:15: error: List item 2 has incompatible type "int"; expected "str"
Found 3 errors in 1 file (checked 1 source file)